Update on Foreman red network while trying to create VM

The configuration is this.

systema : puppet, puppetca, foreman (with proxy)
systemb : foreman-proxy, tftp, dhcp, bind
systemc : esxi 5.0 (60 day license)

Trying to configure a new host, via the esxi, it talks to the proxy ok and
returns the free ip address's. But fails to create the VM and the network
tab goes red. I have turned debug logging on and the message that is put in
the foreman production log is :-

Failed to save: Mac can't be blank, Mac is invalid

But it doesn't expose the mac field as its a vm. I was told
that perhaps there is a restriction on creating VM's using the API on the
60 day license but we have created some with the powercli and its all
working. Has anyone got any ideas ?